ABSTRACT
BACKGROUND: Global variation in human papillomavirus (HPV) prevalence and persistence may be explained by differences in risk factors, such as sexual activity, oral contraceptive use, and behavioral factors. We evaluated determinants of acquisition and clearance of HPV infection among young women previously unexposed to HPV. METHODS: Five hundred thirty-four women aged 15 to 25 years who were cytology and HPV DNA negative, and seronegative for anti-HPV-16/18 antibodies, were recruited (July 2000-September 2001) from study centers in Brazil, the United States, and Canada (NCT00689741/NCT00120848). They were followed up for 76 months. Cervical samples were HPV genotyped via polymerase chain reaction. We used multivariable (forward stepwise, P = 0.15) Cox proportional hazards regression to estimate rate ratios (RR) and 95% confidence intervals (CI), separately according to length of follow-up time. RESULTS: On short-term follow-up (0-27 months), 257 (48%; 8535.80 person-months; incidence rate = 30.11; 95% CI, 26.64-34.02) incident HPV infections were detected. Marital status, lifetime number of sex partners, history of any sexually transmitted disease, and occasional use of oral contraceptives were strongly associated with acquisition of any HPV. Having 2 or more lifetime sex partners (RR, 2.03; 95% CI, 1.37-3.02) and a history of any sexually transmitted disease (RR, 1.98; 95% CI, 1.19-3.29) were the most important determinants of high-risk HPV (hrHPV) incidence. During the entire follow-up (0-76 months), an increased hrHPV clearance was found among women in North America (RR, 1.38; 95% CI, 1.08-1.78) and black women (RR, 1.64; 95% CI, 1.04-2.60). Greater number of lifetime partners was associated with reduced clearance rates for any HPV (RR, 0.65; 95% CI, 0.43-0.98). CONCLUSIONS: We identified variation in risk of HPV acquisition and clearance among women unexposed to HPV at baseline.